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The DOE SciDAC program funded a team that developed PFLOTRAN, the next-generation (‘peta-scale’) massively parallel, multiphase, multicomponent reactive flow and transport code. These codes are required to improve understanding and risk management of subsurface contaminant migration and geological sequestration of carbon dioxide. The important fate and transport processes occurring in the subsurface span a wide range of spatial and temporal scales, and involve nonlinear interactions among many different chemical constituents. Due to the complexity of this problem, modeling subsurface processes normally requires simplifying assumptions. However, tools of advanced scientific computing that have been used in other areas such as energy and materials research can also help address challenging problems in the environmental and geoscience fields. The overall project was led by Los Alamos National Laboratory and included Argonne, Oak Ridge and Pacific Northwest National Laboratories, in addition to the University of Illinois. This report summarizes the results of the research done at the University of Illinois, which focused on improvements to the underlying physical and computational modeling of certain transport and mixing processes.

Glycolic acid is being evaluated as an alternative for formic and nitric acid in the DWPF flowsheet. Demonstration testing and modeling for this new flowsheet has shown that glycolic acid and glycolate has a potential to remain in certain streams generated during the production of the nuclear waste glass. A literature review was conducted to assess the impact of glycolic acid on the corrosion of the materials of construction for the DWPF facility as well as facilities downstream which may have residual glycolic acid and glycolates present. The literature data was limited to solutions containing principally glycolic acid. The reported corrosion rates and degradation characteristics have shown the following for the materials of construction.  For C276 alloy, the primary material of construction for the CPC vessels, corrosion rates of either 2 or 20 mpy were reported up to a temperature of 93 C.  For the austenitic stainless steels, 304L and 316L, variable rates were reported over a range of temperatures, varying from 2 mpy up to 200 mpy (at 100 C).  For 690, G30, Allcorr, Ultimet and Stellite alloys no data were available.  For relevant polymers where data are available, the data suggests that exposure to …

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The lithium silicates have attracted scientific interest due to their potential use as high-temperature sorbents for CO{sub 2} capture. The electronic properties and thermodynamic stabilities of lithium silicates with different Li{sub 2}O/SiO{sub 2} ratios (Li{sub 2}O, Li{sub 8}SiO{sub 6}, Li{sub 4}SiO{sub 4}, Li{sub 6}Si{sub 2}O{sub 7}, Li{sub 2}SiO{sub 3}, Li{sub 2}Si{sub 2}O{sub 5}, Li{sub 2}Si{sub 3}O{sub 7}, and a-SiO{sub 2}) have been investigated by combining first-principles density functional theory with lattice phonon dynamics. All these lithium silicates examined are insulators with band-gaps larger than 4.5 eV. By decreasing the Li{sub 2}O/SiO{sub 2} ratio, the first valence bandwidth of the corresponding lithium silicate increases. Additionally, by decreasing the Li{sub 2}O/SiO{sub 2} ratio, the vibrational frequencies of the corresponding lithium silicates shift to higher frequencies. Based on the calculated energetic information, their CO{sub 2} absorption capabilities were extensively analyzed through thermodynamic investigations on these absorption reactions. We found that by increasing the Li{sub 2}O/SiO{sub 2} ratio when going from Li{sub 2}Si{sub 3}O{sub 7} to Li{sub 8}SiO{sub 6}, the corresponding lithium silicates have higher CO{sub 2} capture capacity, higher turnover temperatures and heats of reaction, and require higher energy inputs for regeneration. Based on our experimentally measured isotherms of the CO{sub 2} chemisorption …